It is a moment that disturbs Ibram X Kendi to this day. It was the 90s, and Kendi – then in his final year of high school – was due to deliver a speech at a public-speaking contest held in Martin Luther King’s honour.

“When we think of American history in the 90s, we’re really talking about the period in which people in both political parties, people ofall races were looking at the increasing violent crimes among black youth, particularly in urban neighbourhoods, as fundamentally caused by a problem with the black youth; the growing percentage of single-parent households,” he says, setting the scene. “We had people thinking that the cause of that was that there was something wrong with young, black mothers.”

Both white and black people thought there was something wrong with black youth: they didn’t value education enough; they were focused on having sex and getting pregnant; they were “not being trained well by their parents”. This was the decade in which black people were labelled “super predators”. These racist ideas had been hammered into Kendi’s skull – and he reproduced them in a speech in front of thousands of predominantly black young people. And they cheered him for it.

“On a day that was supposed to be celebrating black youth – we were a representation about all the things right about black youth – all I could think about was all of the things wrong with black youth. I swallowed those racist ideas whole, because they were largely fed to me by older people,” he says.

Ibram X Kendi: 'Racist ideas have always been murderous' - video

A softly spoken giant with tied‑back dreadlocks, wearing a suit complete with a pocket handkerchief, Kendi is a highly charismatic historian and author who is emerging as one of the pre-eminent intellectuals on race. He was born in Queens, New York, in Ronald Reagan’s US; his parents met in 1970 at a conference focused on black theology, which he describes as “the notions that black Christians should use Christianity as a form and source of liberation, that Jesus is black, that God is black, that the Church needs to be relevant to the black community”. They became Christian ministers and instilled in him this fusion of Christian ideas and black power. As a young child, he saw them discussing constantly how to challenge racism and “ensure that black people could truly be free in the United States”.

As a student he changed his middle name from Henry to Xolani (Zulu for “be peaceful”) after learning about the Portuguese explorer Henry the Navigator’s part in the slave trade. Then, on his wedding day, he and his wife changed their surnames to Kendi, which means “the loved one” in the Kenyan language of Meru, according to the New Yorker.A former journalism student, his PhD dissertation looked at the black radical student movements of the 60s; in 2016, he won the National Book award for Stamped from the Beginning, which aimed to tell “the definitive history of racist ideas in America”.

‘His crime bill led to the greatest mass incarceration of black and brown people in American history’ ... Bill Clinton, then the US president, watches a student police officer at shooting practice in 1994. Photograph: Dirck Halstead/The Life Images Collection/Getty Images

In the age of Donald Trump and rightwing populism, his new book, How to Be an Antiracist could hardly be more relevant. At its core is a superficially simple idea that, somehow, when you read it, feels like a light switch being flicked on: that any genuine opponent of racism has to identify as an anti-racist, not simply as “not racist”. In fact, Kendi believes US history can be seen as a battle between anti-racist and racist ideas.

“I think most people across the world are taught to believe – and believe themselves – to be not racist,” he explains. Even obvious racists often do not self-identify as such, he notes, from slaveowners to colonisers to 21st-century white nationalists. “I am the least racist person there is anywhere in the world,” the racist US president declared in July. “I don’t think people realise that when they self-identify as ‘not racist’, they’re essentially identifying in the same way as white supremacists,” says Kendi.

Proclaiming that you are“not racist” does not require anyone to consider how they should fight racism. To be anti-racist, on the other hand, means developing a philosophy that directly confronts that of a racist.

Racists hold that “certain racial groups are better or worse than others”, Kendi says, while an anti-racist “expresses emotions that the racial groups are equals”. There is no middle ground, he says. We either support systems and policies that promote racial inequality – with enthusiasm, or by our own passivity – or we actively fight them. “So, the term ‘not racist’ not only has no meaning, but it also connotes that there is this sort of in-between safe space sideline that a person can be on, when there is no neutrality,” he explains. “We’re either all being racist or anti-racist.” This is why he wrote this book: he couldn’t define “not racism” and wanted to answer those who asked: “How do I be anti-racist?”

The mainstream media have been one of the historic platforms for racist ideas

What does this mean in practice? For one, reparations for centuries of oppression and systemic injustice against black people has become a mainstream demand of anti-racist movements in the US. It has been caricatured as writing a cheque to African-American citizens, but, in a 2016 manifesto, an umbrella group called the Movement for Black Lives detailed what it could mean: universal access to education for all black people; a guaranteed liveable income; a national curriculum that centres on the legacy of colonialism and slavery; and access and control of food, housing and land. “White median wealth in the United States is about 10 times more than black median wealth, so there’s a massive racial wealth gap,” he says – and it is growing. How is it possible, Kendi asks, to reduce – let alone eliminate – such a gap without reparations? This would be anti-racism in action.

What of the media’s role in legitimising racist ideas and making them mainstream? From Fox News to Britain’s rightwing media, Muslims, migrants and refugees face demonisation and hate. He pauses, smiling gently, choosing his words carefully. “First, the mainstream media should recognise that they have been one of the historic platforms for racist ideas,” he says. “The mainstream media have historically reproduced racist ideas, often not knowing it.”

Then there is the issue of how the far right have attempted to protect hate speech – specifically the right to use public platforms to incite hatred – as “free speech”. Kendi says it is worse than that: just as the second amendment grants Americans the right to possess guns that are then used to kill their fellow citizens, so the first amendment – intended to protect free speech – can safeguard the right to incite racism. “When you put them together, you have mass murder as happened in El Paso.” Kendi refers to the classic debunking of unimpeded speech: yelling “Fire!” in a crowded theatre and causing a fatal stampede. In the face of El Paso, Christchurch, Pittsburgh and Utøya, what counter-argument is there?

One of the misconceptions about Trump is that his victory fell out of a clear blue sky – that state-sanctioned racism is a new phenomenon. Yet it is no accident, Kendi argues, that the Trump era followed the election of the first African-American president: in the Reconstruction era that followed the US civil war, “Radical Republicans” fought passionately for the equality of the formerly enslaved. Then came segregation and the Jim Crow laws, the Ku Klux Klan, lynching and racist oppression. The idea of a “post-racial society”, he believes, merely perpetuates the myth that inequities aren’t caused by racist policies – “because we are post-racial, we no longer have a race problem”.

History is not a story of relentless progress, after all, but of victories followed by setbacks and defeats. “It’s absolutely critical for us to call out Trump’s racism, but we should simultaneously recognise that it is reflective and representative of the history of America and that, if we get rid of Trump, we’re not getting rid of racism,” says Kendi.

Trump has recognised the pervasiveness of anti-black, anti-Muslim and anti-Latinx racism and built a campaign around it. But what of George W Bush – who partly owed his presidency to the disenfranchisement of Florida’s black citizens – and what of his response to Hurricane Katrina? What of Bill Clinton’s 1994 crime bill, which led to “the greatest mass incarceration of black and brown people in American history”, or his “welfare reform”, which disproportionately penalised minorities? What of Reagan, who vetoed sanctions against Apartheid South Africa and used racialised dog whistles such as “welfare queens”, widely seen as feckless, undeserving African-Americans?

What is particularly striking about Kendi’s ideas is how racism and neo-liberalism – which justifies driving back the public realm in favour of the market, deregulation and slashing taxes on the rich – has fused. After the second world war, the consensus in the west was that society was riddled with collective injustices that could be fixed only with collective solutions. That drove the foundation of the welfare state and the NHS in Britain; in the US, it underpinned the “Great Society” and “War on Poverty” of Lyndon Johnson. Then Thatcherism and Reaganism argued that problems such as unemployment or poverty were a question of character and personal, moral failings. “This was a revolution against the idea that the cause of economic and even racial inequities was policies,” Kendi says. “Therefore, these new revolutionaries made the case that the problem was not policies – the problem was people.” It was a convenient means to rationalise growing inequality – those at the top deserved to be there, as did those at the bottom. “The problems were these inferior racial groups – although they didn’t use the term ‘inferior’; they just used dog whistles.”

This lies partly at the root of “whitelash” against the struggles of minorities for equality. As the phrase goes: “When you are accustomed to privilege, equality feels like oppression.” As Kendi puts it: “You already believe equality of opportunity exists, so instead you’re going to reframe equal opportunity as an assault against you and your livelihood.”

It was convenient too, to deflect responsibility from injustices caused by the powerful. When people blame immigrants, Muslims, or black people “as the cause of their own economic and social struggles”, as Kendi puts it, the politicians who have caused injustice are no longer held to account. It also entrenches divisions within the working class – “The working class in the United States has never been united; it’s always been divided along the lines of race” – breaking down the solidarity needed to progress. Kendi is clear, too, that the histories of racism and capitalism can’t be separated. “Racism and capitalism emerged at the same time, in 15th-century western Europe, and they’ve reinforced each other from the beginning.” Slavery and colonialism accumulated the wealth that powered capitalist expansionism. For Kendi, to be an anti-racist is also to be an anti-capitalist.

For all this, Kendi sees hope. In the rise of the Squad – the freshman progressive congresswomen of colour Alexandria Ocasio-Cortez, Rashida Tlaib, Ayanna Pressley and Ilhan Omar – for instance. Trump has engaged in racist onslaughts against them, imploring the women – three of whom were born in the US and all of whom are citizens – to “go back [to] the totally broken and crime infested places from which they came”, while his supporters chanted “Send her back” when he lambasted Omar. The Squad epitomises something particularly threatening, says Kendi – not just for Trumpian Republicans, but many moderate and liberal Democrats, too. “They represent this young, anti-racist movement among people of colour, to challenge and reshape America,” he says. Yet they are hated for being “too young, or too radical, or too dark. And that they will destroy America.” Trump, meanwhile, presents himself as their antithesis, “that there is a fight over America between me and them – who are you going to join?”

So, how to defeat Trumpism? Kendi is in no doubt: racism propelled Trump to victory and anti-racism will defeat him. Although he hasn’t publicly endorsed a Democratic presidential nominee, the policies he advocates are Medicare for All – “A policy that is deeply anti-racist, because black people and other people of colour are disproportionately underinsured or don’t have insurance and are more likely to be sick and die as a result of diseases” – student debt forgiveness and the legalisation of cannabis; all would reduce racial inequality, he says.

It is days since the death of the iconic American essayist and novelist Toni Morrison. Kendi is inspired by her legacy, which has had a profound impact on his writing. “We can’t really separate American literature from Toni Morrison, particularly in the last 50 years.” Indeed, the fact that Morrison helped inspire a new generation of anti-racist writers, such as Kendi, offers hope for a nation in turmoil. Racism, colliding with economic and social injustice, is at the root of the US’s current crisis, but, through the words of Kendi, we have a chance to discover an antidote to the apparently neverending political horror.